Maintenance of mammalian tissue homeostasis and function requires coordinated actions of multiple cellular and molecular networks. This complexity is reflected in the immune system, which is composed of a plethora of cells that constitute the innate and adaptive immune system and which can sense multiple endogenous and exogenous factors. Similarly, the nervous system includes a myriad of distinct neurons that perceive, integrate, and respond to ever-changing environmental conditions. Functional interactions between the neuronal and immune systems have been reported in health and disease, such as in multiple sclerosis, autism, cancer, and chronic inflammatory disorders (1). More recently, a number of studies have revealed that discrete neuronal and immune cells share anatomical localization and interact functionally, forming neuroimmune cell units (NICUs) that orchestrate tissue homeostasis and integrity (2). These findings are provoking a fundamental paradigm shift in our understanding of neuronal–immune cell interactions. A recent noteworthy example is the finding that the nervous system can have a major regulatory effect on multiple innate immune cells with functional impact in several physiological processes (3–8).